paddy is sown in June to September (rainy season). soil is prepared using plough and rake. also, an elaborate system of pipelines and channels has to be devised to carry water to all parts of the field when crops have grown. levelling of soil is also important so that distribution of water in all parts of the field is equal.
To prepare soil for planting
This sentence has a single subject with compound predicate "prepare the soil and ready it for planting."
Farmers plow their fields to break up the soil, making it easier for planting seeds, improving soil aeration and water retention, and helping to control weeds. Plowing also helps to incorporate organic matter into the soil, which can improve soil fertility.
Silts are naturally brought by rivers and streams when they overflow their banks. This process is a natural way for soil to be replenished and fertilized which benefits farmers' fields.
Rice is typically grown in flooded or saturated soil conditions, known as paddy fields, that provide the necessary water and nutrients for the rice plants to grow. The soil is usually clayey or loamy with good water retention capabilities. It is important for the soil to be well-drained to prevent waterlogging.
red soil
Leaving fields unplanted allowed soil to recover from cash crops production, but it was impossible for poor farmers who needed the money from the sale of their crops.
Trees and vegetation have to be cleared first when establishing paddy fields. If the land is hilly, then the landscape is terraced (like a series of steps) as paddy fields have to be flooded with water. Each field is dug out and earth is used to build dykes around the edges. Rice paddy fields are a substantial contributor of methane, a powerful greenhouse gas, as organic matter decomposes anaerobicly under the water. So paddy fields do change the environment in several ways.
to let the soil gain nutrients that it was lost
Actually paddy is a monsoon crop, so it is mostly cultivated in monsoon regions of China, India and Bangladesh.
farmers prepare manures by dumping animal dung, vegetable and crop wastes at open places and let them be decomposed by bacteria and fungi. After a month or so, the manure is ready and is mixed up with soil.
well, by rotating the fields, the farmers give the soil a chance to naturally restore nitrogen and other nutrients.